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Hello!

I have been cleaning the 545B/1A1 and now it shines :-)

Then I have connected it and I have got a curious trace; I have put a
picture of it at:



Center line is Channel 2, connected to GND. The other lines should be a
calibrator signal on Channel 1.

As you can see, the trace goes back and is distorted. It is synchronized
with LINE, so it seems as a power supply filtering trouble. But as I have
no manual nor schematics, I can't work on this easily. Do you have any hint
for this trouble?. Also, if somebody could scan the schematics (or at least
the power supply section) of the 545B it would sure help a lot!

Regards,

JOSE

----------------------------------------------------------------------
73 EB5AGV / EC5AAU - JOSE V. GAVILA
La Canyada - Valencia (SPAIN)

EB5AGV Vintage Radio Site:

European Boatanchors List:

Hi Jose,
It looks like the power supply isn't regulating properly and has
ripple on it.
I'd check the supply lines for ripple if you've got another CRO. Probably
either voltage set too high, weak electrolytics or regulator tubes.
Sorry, I don't have the schematic.
Don Black.


"JOSE V. GAVILA (EB5AGV/EC5AAU)" wrote:

Hi Jose,

I would agree that it looks like a power supply problem. You should be able to
find the test points for the power supplies on a ceramic strip on the upper
chassis toward the rear of the scope. The voltages will be marked on the
chassis (-150, +100, +225, etc.) They should each be within 2% of nominal and
should have only about 5-10 mv of AC ripple on them. The calibrator and both
sweep circuits should be off when checking ripple and you should be able to
vary the line voltage + or - 10% of nominal and still have well regulating
power supplies. In the US, we consider nominal line voltage to be 115VAC and
vary it from 105 to 125 VAC while watching the ripple and voltage on each power
supply with another scope. Both should remain stable.

My guess is that you have 230 VAC and you should vary the mains voltage from
210 to 250 VAC while watching the voltage and ripple on each of the 5 power
supplies (-150, +100, +225, +350, and +500 volts).

Morris Odell mentioned a pull switch in the vertical plugin compartment. This
switch is found in the 547, 546, and 544 but not the 545B and 543B. This means
you MUST have a plugin installed in the 545B for the power supplies to regulate
properly.

You also mentioned that the power switch burned up. Yes, I have seen this many
times. They just develop high contact resistance over time and you need to
replace it. There is nothing special about this switch except that it should
be rated for 10 amps.

With regard to the slow starting of your scope (sometimes NO starting), if you
had a manual, you would see that the heater voltage applied to the delay relay
(looks like a vacuum tube) is applied through a couple of normally closed
contacts on the mechanical relay that eventually closes and allows the scope to
function. If those contacts develop high resistance, the turn-on time will
vary irratically. You should carefully burnish all of the contacts on the
mechanical relay.

Yes, it is normal for some of the internal neons to turn off and on as the
scope warms up and their operation will change again when the mechanical relay
closes.

I have read the other comments and this still sounds like a power supply
problem in the 545B to me . . .

Stan
w7ni@...

JOSE V. GAVILA (EB5AGV/EC5AAU) wrote:

Hi,
I followed this discussion for a while. I have a 1A1 manual
series no. 20000 up with FETs in the input stages. The circuit
between the CH1 input and CH1 output is only supplied by the
-150V, +100V and +225V. I think the "bump" you see see is
supposed to come from one of these 3 voltages. The -150V is the
reference voltage for the whole scope and also for the other
supply voltages. Its one of the first things you need to check
and adjust during a calibration and once it is adjusted you
must never touch it again, or you need to run your calibration
again.
The voltages are supplied through the following pins of the
interconnecting plug: +225V pin11, -150V pin9, and the +100V
runs through the filament of V252 and V261 in the timebase B and
drives a current of about 150mA into pin15 of the interconnecting
plug. This current flows through a voltage divider in the plug in.
The voltage divider supplies +39, +11 and +5V to the plug in.
The voltage at pin 15 is about 75V.
If you need a scan of the 1A1 CH1 input circuit or the 545B
power supply, let me know. I can do that on the weekend.
By the way there is 545B manual on Ebay in Germany. I think its
worth the try to see whether the seller ships it to Spain. If
you can't get it shipped to Spain, let me know.
Leo

--- In TekScopes@y..., Stan or Patricia Griffiths <w7ni@e...> wrote:

Hi Jose,

I would agree that it looks like a power supply problem. You

should be able to

find the test points for the power supplies on a ceramic strip on

the upper

chassis toward the rear of the scope. The voltages will be marked

on the

chassis (-150, +100, +225, etc.) They should each be within 2% of

nominal and

should have only about 5-10 mv of AC ripple on them. The

calibrator and both

sweep circuits should be off when checking ripple and you should be

able to

vary the line voltage + or - 10% of nominal and still have well

regulating

power supplies. In the US, we consider nominal line voltage to be

115VAC and

vary it from 105 to 125 VAC while watching the ripple and voltage

on each power

supply with another scope. Both should remain stable.

My guess is that you have 230 VAC and you should vary the mains

voltage from

210 to 250 VAC while watching the voltage and ripple on each of the

5 power

supplies (-150, +100, +225, +350, and +500 volts).

Morris Odell mentioned a pull switch in the vertical plugin

compartment. This

switch is found in the 547, 546, and 544 but not the 545B and

543B. This means

you MUST have a plugin installed in the 545B for the power supplies

to regulate

properly.

You also mentioned that the power switch burned up. Yes, I have

seen this many

times. They just develop high contact resistance over time and you

need to

replace it. There is nothing special about this switch except that

it should

be rated for 10 amps.

With regard to the slow starting of your scope (sometimes NO

starting), if you

had a manual, you would see that the heater voltage applied to the

delay relay

(looks like a vacuum tube) is applied through a couple of normally

closed

contacts on the mechanical relay that eventually closes and allows

the scope to

function. If those contacts develop high resistance, the turn-on

time will

vary irratically. You should carefully burnish all of the contacts

on the

mechanical relay.

Yes, it is normal for some of the internal neons to turn off and on

as the

scope warms up and their operation will change again when the

mechanical relay

closes.

I have read the other comments and this still sounds like a power

supply

problem in the 545B to me . . .

Stan
w7ni@e...

JOSE V. GAVILA (EB5AGV/EC5AAU) wrote:

Hello!

I have been cleaning the 545B/1A1 and now it shines :-)

Then I have connected it and I have got a curious trace; I have

put a

picture of it at:



Center line is Channel 2, connected to GND. The other lines

should be a

calibrator signal on Channel 1.

As you can see, the trace goes back and is distorted. It is

synchronized

with LINE, so it seems as a power supply filtering trouble. But

as I have

no manual nor schematics, I can't work on this easily. Do you

have any hint

for this trouble?. Also, if somebody could scan the schematics

(or at least

the power supply section) of the 545B it would sure help a lot!

Regards,

JOSE

------------------------------------------------------------------

----

73 EB5AGV / EC5AAU - JOSE V. GAVILA
La Canyada - Valencia (SPAIN)

EB5AGV Vintage Radio Site:

European Boatanchors List:

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